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Keywords:

  • Ascorbic acid;
  • cow milk;
  • HPLC-DAD;
  • vitamin analysis

Summary

An improved extraction (2.5% HPO3, 5 mm dithiothreitol) and HPLC quantification methodology using a C–18 column at 35 °C and 0.1 m acetic acid (98%) and acetonitrile (2%) mobile phase was developed to quantify total ascorbic acid (AA) in commercial whole/semi-skim/skim raw/pasteurised/UHT milk packaged in opaque bags, transparent plastic, cardboard and Tetra Brik. AA content ranged from 0.21 to 10 and from 3.4 to 16 mg L−1 in milk from retail outlets and processing plants, respectively, and was higher in organic milk. For same processor/lot samples, pasteurised milk showed higher AA content than UHT milk. This was not true for retail outlets samples. AA content was similar for whole/semi-skim and semi-skim/skim milk, but not for whole/skim comparisons. Among UHT samples, the AA content trend was whole<semi-skim<skim and lower for UHT milk in opaque plastic and Tetra Brik container. After 14 days at 4 °C in the dark, AA losses ranged 35–83% depending on milk type and preservation method with a higher AA retention in unopened containers.